Selective call signaling systems (e.g., paging systems) provide one-way radio frequency (RF) communication of selective call messages to a selective call receiver. Prior art systems primarily delivered individually addressed messages from a message originator to a unique selective call receiver. The message originator contacts the selective call system via the public switched telephone network system or other input interface means and provides the message information to a selective call terminal. The message information is coupled to address information to form a selective call message. The address information uniquely identifies the selective call receiver. The selective call message is encoded into a conventional signaling protocol, modulated onto a carrier signal, and transmitted as an RF signal to the selective call receiver. The selective call receiver receives the signal, demodulates and decodes the signal to recover the message and address information, correlates the address information with known addresses assigned to the selective call receiver, and presents the message to the system subscriber who is the user of the receiver if the address information positively correlates.
More recently, selective call systems have offered maildrop services which allows the assignment of a common maildrop address to a number of selective call receivers. One such maildrop service is described in U.S. Pat. No. 4,873,519. Maildrop selective call receivers typically have a number of slots reserved for maildrop messages. When a maildrop message is received, it is stored in the corresponding slot, overwriting any maildrop message previously received that was addressed to that slot.
The importance of maildrop services has increased with the advent of information services which provide timely updates of financial, sports, and news information as commonly addressed messages to a number of selective call receivers. Yet, even with the increased importance of maildrop, the maildrop messages when received continue to overwrite previously received messages with the same maildrop address. All information contained in the prior maildrop message is lost to the user. The problem is exacerbated when the user has not read the prior maildrop message before it is deleted.
Thus, what is needed is a selective call receiver which, upon receipt of a maildrop message, does not overwrite a maildrop message previously received on the same address if the previous maildrop message has not been read.